Improvements have been sought for methods of obtaining plasma samples that employ centrifuges and the like equipment used to separate plasma from whole blood and whole blood constituents or fractions such as red blood cells. Emphasis has been placed on the suitability of obtaining plasma samples that are suitable for rapid diagnostic assays used to measure a number of important physiologically active components of whole blood.
U.S. Published Patent Application No. 2008/0210644 describes a blood separator and a method utilizing a glass fiber and paper matrix for separating a fluid fraction from the whole blood. A device for collecting a whole blood sample and for separating a fraction such as plasma therefrom includes two rectangular shell-like pieces that are snapped together, to apply a particular physical stress to a blood separator composite. The device includes a collection port adjacent one end of the glass fiber composite and a second port spaced therefrom to provide access to a glass capillary to extract the fluid fraction separated from the whole blood.
U.S. Pat. No. 7,115,421 discloses a device for the visualization and measurement of hematocrit in a blood sample by separating blood plasma from red blood cells on an absorbent substrate provided with a blood plasma soluble dye.
U.S. Pat. No. 6,258,045 is directed to a collection device for biological samples. The device has a complicated construction and includes the use of capillary collection tubes that further add to the complexity of the device.
U.S. Pat. No. 4,816,224 discloses a device for separating plasma or serum from whole blood. The device includes a relatively complex arrangement, including various layers of glass fibers and the like to process the whole blood.
Despite these and other advances, a need still exists for improved sample collection devices.